Constant speed control device for vehicle

ABSTRACT

A constant speed running control device for automatically holding a vehicle speed constant makes a response of an aimed speed setting signal delayed to the order of that of a vehicle speed meter indication by making a smoothening characteristics of the aimed speed setting signal different from that of a running speed signal so that the running speed is made substantially coincident with an aimed speed desired by a vehicle operator.

FIELD OF TECHNOLOGY

The present invention relates to a constant speed control device for avehicle for automatically holding a running speed of the vehicle at aconstant value.

BACKGROUND ART

An example of known constant speed control device for a vehicle is shownin FIG. 1. That is, FIG. 1 shows a conventional constant speed controldevice disclosed in, for example, Japanese Patent Application Laid-openNo. 39811/1983, in which 1 depicts a set switch responsive to anoperation of a vehicle operator to start a constant speed running, 2 acancelling switch responsive to an actuation of a braking device (notshown) to terminate the constant speed running and 3 a speed sensor fordetecting a running speed of the vehicle, which comprises a rotarymember 3a having four magnetic poles and adapted to be rotated by ameter cable (not shown) for transmitting rotation of a vehicletransmission (not shown) and a reed switch 3b and produces a series ofpulses having a frequency proportional to a running speed. 4 depicts avehicle mounted battery, 5 a main switch which is a power source switchfor supplying electric power from the battery 4, and 6 a control devicehaving a processing circuit 6a including a microcomputer etc. and issupplied with electric power by closing the main switch 5. The controldevice is responsive to signals from the set switch 1, the cancellingswitch 2 and the speed sensor 3 to perform various operations necessaryto automatically equalize an actual running speed Vs to an aimed speedVr and to output various control signals. 7 depicts a motor-driventhrottle actuator responsive to the various control signals from thecontrol device 6, 8 a suction passage of an engine and 9 a throttlevalve provided in the suction passage 8 and ganged with an accelerationpedal (not shown). The throttle valve is driven in open and closedirections by a link 7a and a wire 7b of the throttle actuator 7. Arotation angle of the link 7a corresponding to the degree of opening ofthe throttle valve 9 is detected by a potentiometer (not shown) housedtherein and given to the control device 6 as a signal indicative of athrottle position. The link 7a and a motor for driving the throttleactuator are connected to each other by an electromagnetic clutch (notshown and disconnected from each other by an electromagnetic clutchsignal from the control device 6.

In operation, when the main switch 1 is closed by the vehicle operatorand electric power is supplied from the battery 4, the control device 6commences its operation to process an output of the speed sensor 3 whichis a series of pulses having a frequency proportional to the vehiclespeed V. The control device 6 measures a pulse period of the output ofthe speed sensor 3 to obtain an actual speed Vs. The operator operatesthe set switch 1 to supply the speed signal to the control device 6which stores the value Vs as the aimed speed Vr and commences a constantspeed control.

Thereafter, the control device 6 compares the aimed speed Vr with theactual speed Vs obtained from time to time and provides a control signalwith which the throttle actuator 7 is driven to regulate the opening ofthe throttle valve 9 to thereby make the actual vehicle speed coincidentwith the aimed speed Vr. That is, when the actual speed Vs is lower thanthe aimed speed Vr, the control device 6 provides a throttle open signalto drive the throttle valve to a desired position and, when the actualspeed Vs is higher than the aimed speed Vr, provides a throttle closesignal to close the valve 9 suitably. Thus, it is possible to make thevehicle speed constant without an acceleration pedal operation by theoperator. When the operator actuates the brake device while suchconstant speed control is performed, the cancelling switch 2 is actuatedto supply a termination signal to the control device 6 for terminatingthe constant speed control. Upon the termination signal, the controldevice 6 provides a disconnection signal for disconnecting theelectromagnetic clutch, immediately, upon which the throttle actuator 7disconnects the electromagnetic clutch. Thereafter, the operator isallowed to control the vehicle speed by regulating the throttle openingby means of the acceleration pedal.

In the conventional constant speed control device constructed as above,when the set switch 1 is operated to make the vehicle speed constant,the speed signal obtained by the control device 6 on the basis of theoutput of the sensor 3 is not coincident with a value indicated on aspeed meter mounted on the vehicle. The reason for this is that thespeed signal which is used to perform the constant speed control must behighly responsive to the vehicle speed while the response of the speedmeter is intensively lowered since, otherwise, a vibration of indicatorneedle occurs which is uncomfortable for the operator. Therefore, thevehicle may run at a speed other than that set by the operator accordingto an indication on the speed meter. Particularly, an aimed speed tendsto be much different from that indicated on the speed meter after anautomatic acceleration or deceleration is performed by means of switchesetc. other than the acceleration pedal during running at a constantspeed.

SUMMARY OF THE INVENTION

The present invention was made to solve these problems and an object ofthe present invention is to provide a constant speed control devicewhich minimizes a difference between an aimed speed and a speedindication of a vehicle mounted speed meter, and therefore make thevehicle possible to run at a desired speed.

The constant speed control device for a vehicle according to the presentinvention comprises an aimed speed signal generator which receives aspeed signal and produces, in addition to a first smoothened speedsignal to be used for a control, a second smoothened speed signal bypassing the speed signal through a second smoothing means having asmoothing characteristics of the same level as that of a speed meterindication, when an aimed speed setting signal is inputted. With suchscheme of the present invention, it is possible to make an aimed speeddesired by an operator substantially coincident with a control speedsince the aimed speed setting signal generator provides a speed similarto an indication of the speed meter of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an overall construction of a conventional constant speedcontrol device, FIG. 2 shows a block diagram of the present inventionand FIGS. 3 to 6 show, an embodiment of the present invention, in whichFIG. 3 is an overall construction thereof, FIGS. 4(a)-(c) are flowcharts showing the operations of a microcomputer used in FIG. 3, FIG. 5is an output waveform of a speed sensor used in FIG. 3 and FIG. 6 is atime chart showing a running speed, an aimed speed, control signals y₁and y₂ and an operation of a throttle valve.

BEST MODE FOR PRACTICING THE PRESENT INVENTION

The present invention will be described in detail with reference to thedrawings.

FIG. 2 shows a block diagram of the present invention, in which 3depicts a running speed detection means for detecting a running speed ofa vehicle, 10 a first smoothening means for smoothing a running speedsignal V and reducing noise component thereof, 11 an accelerationoperating means for obtaining an acceleration signal α from a smoothenedrunning speed signal Vs every predetermined time, 12 an instructioninformation detection means for detecting an instruction information ofan operator, 13 a second smoothing means having a smoothingcharacteristics similar to a speed meter indication for smoothing therunning speed signal, 14 an aimed speed setting signal generator forsetting the running speed signal passed through the second smoothingmeans as an aimed speed signal Vr when the instruction informationsignal is supplied, 15 a speed deviation operating means for outputtinga speed deviation signal ε from the aimed speed signal Vr and thesmoothened running speed signal Vs and 16 a control amount outputtingmeans for operating a control signal y from the speed deviation signal εand the acceleration signal α. The control amount operating means 16actuates a throttle valve driving means 7 serving as a control means forcontrolling a driving force of the vehicle on the basis of the controlsignal y to drive a throttle valve 9 to regulate an engine output power.In this manner, it becomes possible to run the vehicle at a constantspeed substantially equal to an indicated speed on the speed meter bysetting the aimed speed Vr by using the speed signal passed through thesecond smoothing means having substantially the same smoothingcharacteristics as that of the speed meter when the running mode isshifted to the constant speed mode.

Concrete embodiments of the present invention will be described withreference to FIGS. 3 to 6. In FIG. 3 in which same reference numerals asthose used in FIG. 1 depict same components, respectively, a runningspeed detecting means 3 corresponds to the speed sensor 3 and aninstruction information detecting means 12 corresponds to the set switch1 and the cancelling switch 2. A control device 6 comprises amicrocomputer (FIG. 3) constructed with a first smoothing means 10, anacceleration operating means 11, a second smoothing means 13 and acontrol amount operating means 16 (FIG. 2) and is started to operateupon closure of the main switch 5. The microcomputer includes an inputcircuit 6a having inputs supplied with signals from the set switch 1,the cancelling switch 2 and the speed sensor 3, a memory 6b including aROM and a RAM storing command programs, an output circuit 6c providingcontrol signals and a CPU 6d operable according to the command programsin the memory 6b to process the signals from the input circuit 6a andprovide an output to the output circuit 6c. 17 depicts anelectromagnetic valve to be controlled by a control signal y₁ of themicrocomputer 6 such that an output tube 17a connected to a negativepressure source (not shown) is connected to an input tube 17a when thecontrol signal y₁ is "H" level as shown by an arrow A and isdisconnected therefrom when it is "L" level. 18 is anotherelectromagnetic valve to be controlled by a control signal y₂ such thatan input tube 18a opened to atmosphere is connected to an output tube18b as shown by an arrow B when the control signal y₂ is "L" level andis disconnected therefrom when it is "H" level. 19 is a diaphram deviceconnected to the input tube 17a of the electromagnetic valve 17 and tothe output tube 18b of the electromagnetic valve 18 for driving athrottle valve 9 through a wire 19a, which includes a container 19cforming an air chamber 19b connected to the input tube 17a and the ouputtube 18b, a diaphram 19d mounting the wire 19a thereon and a spring 19edisposed between the diaphram 19d and the container 19c for biasing thediaphram 19d in the shown direction and constitutes, together with theelectromagnetic valves 17 and 18, a throttle valve driving means 7. Thethrottle valve driving means 7 has three operation modes such as shownin Table 1. When both of the control signals y₁ and y₂ are "H" level,the elecromagnetic valve 17 is opened and the electromagnetic valve 18is shut. Therefore, the air chamber 19b is connected to only thenegative pressure source, so that the diaphram 19d moves leftwardly andthus the throttle valve 9 is opened to establish an acceleration mode.When both of the control signals y₁ and y₂ are "L" level indicating adeceleration mode, the electromagnetic valve 17 is shut and theelectromagnetic valve is opened. Therefore, the air chamber 19b isopened to atmosphere, so that the diaphram 19d moves rightwardly bymeans of the spring 19e and thus the throttle valve 9 is closed todecelerate the vehicle. In a holding mode in which the control signal y₁is "L" level and the control signal y₂ is "H" level, the electromagneticvalves 17 and 18 are closed, so that the air chamber 19b is notconnected to either the negative pressure source or atmosphere and thusthe diaphram 19d is held in its position, so that the opening of thethrottle valve 9 is also held in its state.

                  TABLE 1                                                         ______________________________________                                        operation mode y.sub.1 y.sub.2 throttle vale                                  acceleration   H       H       open                                           deceleration   L       L       close                                          holding        L       H       constant                                       ______________________________________                                    

An operation of the embodiment shown in FIG. 3 will be described.Firstly, when the main switch 5 is closed, the microcomputer device 6starts to execute a main routine shown in FIG. 4a. On the other hand, ifthe vehicle is running, the speed sensor 3 thereof produces a series ofpulses having a frequency proportional to a running speed as shown inFIG. 5, which causes the microcomputer device 6 to perform an interruptroutine processing shown in FIG. 4b. That is, the processing in FIG. 4bis performed at every leading edge of pulse of the pulse signal shown inFIG. 5 by reading a time instance t_(n) of the leading edge from a timer(not shown) in the step 201 and obtaining a difference Δt (=t_(n)-t_(n-1)) between t_(n) and t_(n-1) at which a leading edge of apreceding pulse is inputted, i.e., a pulse period in the step 202.Thereafter, the operation is returned to the main routine in FIG. 4a.The running speed can be obtained from a reciprocal of the pulse period,as to be described later. Then, when an operator of the vehicleoperates, during running, the set switch 1 to start the constant speedrunning, the microcomputer device 6 receives the fact in step 102 shownin FIG. 4a. When the microcomputer device 6 decides that it is thesignal from the set switch 1 in the step 103, it makes a flag ACF "H"indicating the constant speed running, in the step 104.

In the step 105, a signal Vr_(n) for an aimed speed, which is to bedescribed later, is used for an aimed speed Vr_(o). On the other hand,in the step 106, it is checked whether or not there is an input from thecancelling switch. If yes, a cancelling operation for cancelling theconstant speed control, i.e., a processing to hold both of the controlsignals y₁ and y₂ in "L" level, is performed in the step 107. In thestep 108, the ACF flag is made "L". In the step 109, a flag indicatingexistence of the control signal is made "L". In the step 110, it ischecked whether or not the switch input information indicates anautomatic acceleration. If yes, a predetermined value e is inserted intoa control amount T in the step 111. In the step 112, it is checkedwhether or not it is an automatic deceleration and, in step 113, it ischecked whether or not the ACF flag is "H".

In the step 114, a current running speed Vn is obtained from the newestpulse period ΔT which was obtained by the interrupt routine in FIG. 4b,according to the following equation. ##EQU1## where N is a constant fortransformation to speed and n is a current value. In the step 115, thesignal Vr for aimed speed is obtained by using a digital filteraccording to the following equation

    Vr=a·Vr.sub.n-1 +b·Vn

where a and b are constants selected such that a variation indicatessubtantially the same order as that indicated by the vehicle speedmeter, and n-1 means a preceding value. In the step 116, the runningspeed Vs is obtained by using a digital filter according to thefollowing equation

    Vs=c·Vs.sub.n-1 +d·Vn

where c and d are constants satisfying c<a and d>b which indicate alow-pass filter characteristics having a cut-off frequency for therunning speed Vs higher than that for the signal Vr for the aimed speed.In step 117, an acceleration signal α of the vehicle is obtained by therunning speed Vs according to the following equation ##EQU2## In step118, a speed deviation signal ε is obtained by the aimed speed Vro andthe running speed Vs according to the following equation

    ε.sub.n =Vro-Vs

In the step 119, it is checked whether or not the vehicle is in theconstant speed running state. If yes (ACF="H"), then it is checkedwhether or not the control signal exists in the step 120. If the controlsignal does not exist, an operation of control amount to regulate theopening degree of the throttle valve 9 is performed in the step 121. Anexample of this operation is to obtain the control amount by using thespeed deviation signal ε and the acceleration signal α according to thefollowing equation

    T=k.sub.1 ·ε.sub.n +k.sub.2 ·α.sub.n

where k₁ and k₂ are constants. With the output time T thus obtained,output levels of the control signals y₁ and y₂ are obtained from theTable 2 according to the sin of the time T and a timer (not shown) isstarted, in the step 122. In the step 123, it waits until time Tolapses, and, after the time To, it is returned to the step 102 andrepeats the respective steps in the same sequence.

                  TABLE 2                                                         ______________________________________                                        T           Control Mode    y.sub.1 y.sub.2                                   ______________________________________                                        positive    acceleration mode                                                                             H       H                                         negative    deceleration mode                                                                             L       L                                         0           holding mode    L       H                                         ______________________________________                                    

When the control signal is provided in the step 122 and the timer countcoincides with the output time T, a timer interrupt routine shown inFIG. 4c is performed. In the step 301, an output level of the holdingmode is set and, in the step 302, the control signal flag is made "L"and the operation is returned to the main routine.

In this manner, the acceleration mode output or deceleration mode outputof the output time T is supplied from the microcomputer device 6 to thethrottle valve driving means 7 and, in the acceleration mode, the airchamber 19b of the diaphram device 19 is shrinked and the diaphram 19dis moved leftwardly thereby to open the throttle valve 9 to apredetermined position. In the deceleration mode, the air chamber 19b isexpanded and the diaphram 19d is moved rightwardly thereby to close thethrottle valve 9 to a predetermined position. An example of the abovementioned operation is shown in FIG. 6. In this figure, it is assumedthat, where the vehicle runs at a desired speed after the automaticacceleration, the running speed Vs is varied as shown by a solid line inFIG. 6a. A dotted line in FIG. 6a shows the running speed obtained byproviding the second smoothening characteristics thereto, which is thesame as that indicated on the speed meter. FIG. 6b shows an accelerationswitch signal for providing an acceleration instruction, and it isassumed that the acceleration signal is provided at a time instance tland terminated at a time instance t2 and the vehicle runs at a runningspeed Vrl at the time instance t2 thereafter. The control signals y₁ andy₂ for such running condition become as shown in FIGS. 6c and 6d,respectively. Therefore, the opening degree of the throttle valve iscontrolled as shown in FIG. 6e. A dotted line in FIG. 6a showscharacteristics of the conventional device, in which the aimed speedafter acceleration becomes Vr₂, as a result, the running speed becomeshigher than that the operator desires.

As described, it is possible to run the vehicle at a constant speedequal to the aimed speed by the use of the signal for the aimed speedfor setting the aimed speed.

Although, in the described embodiment, the constant opening control inwhich the throttle valve is opened to the predetermined position when anautomatic acceleration has been used, it is possible to use a constantacceleration control. Further, although the digital filter is used toobtain the aimed speed setting signal, it is possible to obtain thesignal by using an analog filter. Further, although the throttle valvedriving means 7 is constituted with the electromagnetic valves 17 and 18and the diaphram device 19, it may be replaced by the conventionaldevice using a motor. Further, the acceleration. operation means is notalways necessary for attainment of the object of the present invention.

As described hereinbefore, according to the present invention, by makingthe smoothening characteristics of the aimed speed setting signaldifferent from that of the running speed signal to be used for controlpurpose, the aimed speed setting signal can indicate substantially thesame order of variation as that indicated on the vehicle speed meter andthus it is possible to run the vehicle at a constant speed the operatordesired.

We claim:
 1. A constant running speed control device for a vehiclehaving a speed meter, comprising:running speed detecting means (3) fordetecting a running speed of the vehicle; first smoothing means (10),coupled to receive the output of said detecting means, for reducing anoise component of a running speed signal obtained by said running speeddetecting means; instruction information detecting means (12) fordetecting instruction information inputted by an operator of thevehicle, the inputted instruction information representing a desiredconstant running speed; second smoothing means (13) for receiving theoutput of said running speed detecting means, said second smoothingmeans having smoothing characteristics substantially similar to responsecharacteristics of the speed meter for smoothing said running speedoutput; an aimed speed signal generator means (14) for generating anaimed speed signal Vr based on said smoothed running speed output fromsaid second smoothing means and on said instruction information; speeddeviation operating means (15) for obtaining a speed deviation based onsaid aimed speed signal and said smoothed running speed signal (Vs) fromsaid first smoothing means; control amount operating means (16) foroutputting a control signal based on said speed deviation signal; anddriving force controlling means (7, 9) for controlling a driving forceof the vehicle based on the control signal outputted by said controlamount operating means.
 2. The constant running speed control device asdefined in claim 1, further comprising an accelerating operating means(11), coupled between said first smoothing means and said control amountoperating means, for generating an acceleration signal representing anacceleration of the vehicle running speed signal, said control operatingmeans outputting the control signal based on the speed deviation signaland the acceleration signal.
 3. The constant running speed controldevice as defined in claim 1, wherein said driving force controllingmeans comprises a throttle valve driver (7) and a throttle valve (9),said throttle valve driver controlling a position of said throttle valveaccording to the control signal from said control amount operatingmeans.
 4. The constant running speed control device as defined in claim1, wherein said first and second smoothing means are digital filters. 5.A constant running speed control system for a vehicle, the vehiclehaving a speed meter for displaying a running speed of the vehicle, thedevice comprising:running speed detecting means (3) for detecting therunning speed of the vehicle; smoothing means (13) connected to receivethe output of said running speed detecting means for smoothing saidvehicle running speed, said smoothing means having smoothingcharacteristics which are substantially similar to responsecharacteristics of the speed meter; instruction information detectingmeans (12) for detecting instruction information inputted by an operatorof the vehicle, the instruction information representing a desiredconstant vehicle running speed; an aimed speed signal generating means(14), connected to receive the output of said instruction informationdetecting means and the smoothed running speed from said smoothingmeans, for generating an aimed running speed (Vr) representing thedesired constant vehicle running speed; speed deviation operating means(15), coupled to said running speed detecting means and to said aimedspeed signal generating means, for outputting a speed deviation signal(ε) representing a difference between the detected vehicle running speed(V) and the aimed running speed; control amount operating means (16) forgenerating a control signal based on the speed deviation signal; anddriving force controlling means (7, 9) for controlling a driving forceof the vehicle based on said control signal so that the vehicle runningspeed becomes substantially equal to the aimed running speed.
 6. Theconstant running speed control system as defined in claim 5, furthercomprising noise smoothing means (10) for reducing noise in the outputof said running speed detecting means, said speed deviation operatingmeans outputting a speed deviation signal representing a differencebetween the output of said noise smoothing means and the aimed runningspeed.
 7. The constant running speed control system as defined in claim5, further comprising an accelerating operating means (11), coupledbetween said smoothing means and said control amount operating means,for generating an accleration signal (α) representing an acceleration ofthe vehicle running speed signal, said control operating meansoutputting the control signal based on the speed deviation signal andthe acceleration signal.
 8. The constant running speed control system asdefined in claim 5, wherein said driving force controlling meanscomprises a throttle valve driver (7) and a throttle vale (9), saidthrottle valve driver controlling a position of said throttle valveaccording to the control signal from said control amount operatingmeans.
 9. The constant running speed control system as defined in claim6, wherein said smoothing means and said noise smoothing means aredigital filters.